Turnbuckle

ABSTRACT

A method for manufacturing a turnbuckle mechanism in which a central link is provided with internal right and left hand compatible threads and which receives, at its opposite ends, one of a pair of longitudinally split, externally threaded shafts which are threaded in opposite directions. The split shaft members are manufactured from oppositely threaded cylindrical shafts which are machined along their threaded sections to split each cylindrical shaft into two symmetrical, longitudinally split shaft members, which are then paired with oppositely threaded split shaft members and secured together with the central link, preferably with a separation band of plastic or corrosion resistant metal between their opposing flat surfaces. The shaft members are also provided with distal clamps such as hooks, loops or full threads for attachment of cables, rods or similar members.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to a turnbuckle and, in particular, to aturnbuckle which has an unlimited degree of expansion and contraction,and which eliminates cable twisting.

2. Brief Statement of the Prior Art

Turnbuckles are commonly used to secure the ends of cables, rods orother members, with a variable tensioning capability. A turnbuckle has acentral link having opposite ends which are internally threaded withopposite oriented threads which receive compatibly threaded shaftsbearing distal clasps such as hooks or loops. Rotation of the linkmember thereby extends or contracts the threaded shafts in the assembly,thus providing for variable tensioning of cables, etc. which are securedby the distal clasps of the shaft members.

There are a number of shortcomings in the conventional turnbuckle. Theturnbuckle is awkward and difficult to use since the distal ends of theshafts are commonly attached to cables and the like which do notrotationally restrain the shafts. Consequently, adjustment of thetension on the cables by advancing or retracting the shafts in the linkmember usually requires one to grasp the shaft members, immobilizingthese members while rotating the link member. Alternatively, one rotatesthe link member and entire assembly until sufficient torsion isdeveloped in the cables to restrain the shafts, permitting theirrotational movement in their threaded engagement with the link member.Another disadvantage of the conventional turnbuckle is that it has onlya limited degree of expansion and contraction. Commonly the shafts arecoaxial and their maximum travel in the assembly is no greater than onehalf the length of the link member and, commonly less as the link memberoften has a center rib which obstructs the inward movement of theshafts, The conventional turnbuckle is also bulky with a heavy, castlink member.

OBJECTIVES OF THE INVENTION

It is an objective of this invention to provide a turnbuckle which canbe readily expanded or contracted simply by rotation of the link;

It is also an objective of this invention to provide a turnbuckle withunlimited degree of extension and contraction;

it is likewise an objective of this invention to provide a turnbucklemechanism which can be readily incorporated in linear motion mechanisms;and

It is an additional objective of this invention to provide a turnbucklemechanism for synchronous reciprocal movement of two members

It is a further objective of this invention to provide a turnbucklewhich avoids twisting of cables.

BRIEF DESCRIPTION OF THE INVENTION

This invention comprises a turnbuckle mechanism in which a central linkis provided with internal right and left hand compatible threads andwhich receives, at its opposite ends, one of a pair of longitudinallysplit externally threaded shafts which are threaded in oppositedirections. The shafts are coaxially received in the internally threadedbore of the link and have distal clasps such as hooks or loops forattachment of cables, or other members such as rods or chains.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the figures of which:

FIG. 1 is a perspective view of a turnbuckle according to the invention;

FIG. 2 is an enlarged view of the area within line 2-2′ of FIG. 1;

FIG. 3 is a longitudinal, cross sectional view of the link of theturnbuckle of FIG. 1;

FIG. 4 is a longitudinal, cross sectional view of alternative link tothat shown in FIG. 3.

FIGS. 5 and 6 are perspective views of alternative links useful in theturnbuckle shown in FIG. 1.

FIG. 7 is a perspective view of a link useful as an armature of anelectrical motors

FIG. 8 is a view of a turnbuckle having an expansion/contractiondistance limited only by the length of the threaded shaft members.

FIG. 9 is an enlarged view of the area within line 9-9′ of FIG. 8.

FIG. 10 is a perspective view of an alternative turnbuckle.

FIGS. 11-14 illustrate the steps of manufacturing the shaft members forthe alternative turnbuckle shown in FIG. 10.

FIG. 15 is a view of the shaft members formed from the manufacturingsteps shown in FIGS. 11-14.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, there is illustrated a turn buckle 10 according tothe invention. The turnbuckle 10 has a central link 12 in the form of anelongated nut bearing wrench flats 14 on its exterior surface. In theillustration, the link 12 is hexagonally flatted. The internal throughpassage of the link 12 is threaded with right and left hand compatiblethreads coextensive its length, in a manner described and illustrated ingreater detail in FIG. 3 Received in opposite ends 16 and 18 of the link12 are shafts 20 and 22 having distal attachments such as hook ends,although other clasps such as loops or eyes, or even full threads can beused. Since rotation of the link 12 does not cause rotation of theshafts 20 and 22, these shafts can have threaded ends which are receivedin internally threaded nuts or tapped bores, thereby serving as claspmeans. Each shaft has a longitudinally split half section 26 with asemicircular cross section which is externally threaded with either lefthand threads 28 for shaft 20 or right hand threads 30 for shaft 22. Theillustrated turnbuckle 10 is shown in a partially contractedconfiguration with the ends of each of the shafts 20 and 22 projectingthrough and beyond the opposite end of the link 12 thus illustrating thesliding relationship of the two shafts 20 and 22.

Referring now to FIG. 2, the external threaded appearance of the shaftmembers is apparent and, as shown, the upper shaft 22 bears right handthreads 30 while the lower shaft 20 bears left hand threads 28. Thethreads are of the same pitch and depth, i.e., are identical exceptbeing oriented in opposite directions.

Referring now to FIG. 3, there is illustrated a longitudinal sectionalview of the link 12. As previously mentioned, the link 12 is in the formof an elongated hexagonally flatted nut and has a central bore 32 whichis internally threaded with right hand threads 30 and with left handthreads 28 coextensive its entire length. This permits the l threadedshafts 20 and 22 which coact to restrain each other as the link 12 isrotated thereby permitting a simple single-handed expansion andcontraction of the assembly simply by rotation of the link 12.

Referring now to FIG. 4, the link 12 can have, at its opposite ends 16and 18, an unthreaded section 34 and 36 to facilitate orientation of theshafts 20 and 22 when they are initially installed in the link 12. Theunthreaded sections 34 and 36 serve to orient the shafts 20 and 22axially in the assembly, facilitating the initial engagement of theseshafts.

Alternatively, the shaft members can have distal threads 38 upset asshown on FIG. 1, thereby preventing their complete removal from theassembly.

Referring now to FIG. 5, there is illustrated a perspective view of analternative link 40 which is provided with a hand tensioning wheel 50 ofgreater diameter than the body of the link member which can be providedwith external grooves 52 for increased frictional grasping by a user.

Alternatively, the link member can be provided with external gear teethas shown in FIG. 6, in which the link 54 has a central circular flange56 bearing a circumferential row of gear teeth 58 to be engaged by asuitable gear or rack drive in a gear drive. In this manner, theturnbuckle of the invention can be adopted to translate rotary motion toreciprocating, reverse, linear movement.

Referring now to FIG. 7, the link can be externally configured as anarmature of a conventional electric motor in which the link 60 has acentral cylindrical body 62 with its external cylindrical surface 64bearing evenly spaced splines 66 as conventional for armatures.Additionally, the opposite ends 68 and 70 of the link 60 are providedwith stub shafts 72 which can be received in the bearing journals of anelectric motor. The central through bore of the link 60 is threaded withright and left hand threads in the manner described with reference toFIGS. 3 and 4.

FIG. 8 illustrates an embodiment in which the shaft members 78 and 80are split their entire lengths, thereby permitting the threaded shaft ofeach shaft member 78 and 80 to be fully advanced or retracted by thelink 76, thus achieving an extendible range from a distance equal to thelengths of the link and end eyes 82 and 84 to a full extension equal tothe sum of the lengths of the shaft members 78 and 80 less twice thelength of the link 76.

FIG. 9 is an enlarged view of the turnbuckle shown in FIG. 8. This alsoillustrates the preferred manufacture wherein the shaft members areformed as conventional threaded shafts which are then split by suitablemachining. Examples of various machining techniques which can be usedinclude sawing, EDM machining, laser jet cutting and cutting with a highpressure water jet which includes an abrasive powder suspended in thewater. The latter technique is preferred for cost and efficiency, Thesemachining techniques result in removing a thin layer of metal, forming athin gap between the smooth opposing flat surfaces of the right and leftshaft members. Typically this gap has a thickness from 0.02 to about0.04 inch, usually from 0.025 to 0.030 inch. Preferably, this gap isfilled with a band of a low friction material which can be of plasticssuch as Teflon, on resistant metal such as stainless steel, copper, etc.This is shown in FIG. 9 as a thin flat band 74, which can extend thelength of the shaft members 78 and 80; see FIG. 8. The band 74 isattached or bonded to either one of the two shaft members and for thispurpose mechanical attachment or bonding with adhesive or welding can beused, as appropriate for the application and materials. The width of theband 74 can also be varied as desired to provide a control of the degreeof self-locking of the mechanism with thick bands providing greaterself-locking than thin bands.

Referring to FIG. 10, there is illustrated a turn buckle 11 which is analternative to that shown in FIG. 1. The turnbuckle 11 has a centrallink 12 which can be the same as that shown in FIG. 1, with hexagonalflats 14 on its exterior surface. As with link 12 of FIG. 1, theinternal through passage of the link 12 is threaded with right and lefthand compatible threads coextensive its length. Received in oppositeends of the link 12 are shafts 21 and 23 having distal attachments suchas hook ends 25, although other clasps such as loops or eyes, or evenfull threads can be used. Each shaft has two substantially identical,longitudinally split quarter sections 27 spaced at opposite, or 180degree angular spacing thereby forming two 90 degree slots which receivethe quarter sections of the opposing shaft. The quarter sections areprovided with left hand threads 29 for shaft 21 or right hand threads 31for shaft 23. The illustrated turnbuckle 11 is shown in a partiallycontracted configuration with the ends of each of the quarter sectionedshafts 21 and 23 projecting through and beyond the opposite end of thelink 12 thus illustrating the sliding relationship of the two shafts 21and 23. The shafts 21 and 23 with the illustrated longitudinally quartersplit ends can be fabricated by molding of a suitable polymer, e.g.,Nylon, or can be cut from a single threaded shaft by machining with ajet of high pressure water or aqueous cutting fluid.

FIGS. 11-14 illustrate the fabrication of the turnbuckle members. InFIG. 11, a threaded blank shaft 92 is supported beneath a cuttingelement such as a high pressure jet cutting tool 90 which directs astream 94 of aqueous cutting fluid against the shaft while the shaft isrotated 90 degrees as shown by arrowhead line 96. Alternatively, a lasercutting tool can be used. This forms two, 90-degree sector slots such as98 in the shaft. For illustration purposes, the thicknesses of the slotswhich are formed by the cutting tool is exaggerated. The shaft is thenmoved axially relative to the cutting tool 90 as shown by the arrowheadline 97 in FIG. 12, cutting an axial slot 100 through the shaft. Theshaft is then rotated 90 degrees as shown by the arrowhead line 96 ofFIG. 13 forming 90-degree sector slots such as 102 in the shaft. In thefinal cutting step shown in FIG. 14, the shaft is moved axially relativeto the cutting tool 90 as shown by arrowhead line 99. This forms anaxial slot 104 which intersects the sector slot 98 cut in the firststep, shown in FIG. 11. The last step severs the shaft 92 into twoturnbuckle members 108 and 110 which are shown separated in FIG. 15.Each member 108 and 110 has identical, longitudinally split quartersections, 112 and 114 for member 108 and 116 and 118 for member 110.These longitudinally split quarter sections are spaced at opposite, 180degree angular spacing. The quarter sections 112 and 114 of shaft member108 are complimentary to the quarter sections 116 and 118 of shaftmember 110 thereby permitting the longitudinal engagement of the members108 and 110. Both members 108 and 110, however, have exterior threads ofthe same direction, i.e., if shaft 92 has right hand threads, bothmembers 108 and 110 will have right hand direction threads. The cuttingsteps are also performed on shafts with threads of opposite direction,e.g., left-hand threads, and then one member formed by cutting a shaftwith right-hand threads is paired with a member having complimentaryquarter sections which is formed by cutting a shaft with left-handthreads and the pair are secured together with a link 12 shown in FIGS.1 and 10. Fasteners, such as hooks, eyelets, nuts, etc., can be threadedonto the full shaft ends of the members 108 and 110.

An advantage of the invention which facilitates fabrication is that theshaft members can be provided with any of a wide variety of distalattachments such as hooks, loops or full threads for attachment ofcables, rods or similar members.

Another advantage of the invention is that it provides for reverse,linear movement of the two shaft members in amounts limited only by theshaft lengths of these members. This is illustrated in FIG. 8 in which alink 76 receives opposite shaft members 78 and 80 and their entirelengths, thereby permitting sliding movement of each shaft member pastthe other and providing a turnbuckle mechanism capable of contractionand expansion through distances substantially the entire combined lengthof the shaft members.

The invention has been described with reference to the illustrated andpresently preferred embodiment. It is not intended that the invention beunduly limited by this disclosure of the preferred embodiment. Instead,it is intended that the invention be defined by the means, and theirobvious equivalents, set forth in the following claims.

What is claimed is:
 1. The method for the manufacture of a turnbuckle formed of complementary right and left split shaft members, each bearing a section of helical threads of opposite direction to the threads of the other which comprises: a. cutting complementary right and left threaded sections on cylindrical shafts of equal diameter; b. machining each of said right and left cylindrical shafts to split each longitudinally along said threaded sections to form longitudinally split shaft members having right and left directional helical threads; c. pairing one each of split shaft members with another having opposite directional helical threads; d. placing a separation band selected from low frictional characteristic plastics or corrosion resistant metals between the mating surfaces of said split shaft members; and e. joining said split shaft members with a nut remember having complementary internal right and left directional threads.
 2. The method of claim 1 wherein said threaded cylindrical shafts are split by applying a high pressure jet of water to said shafts.
 3. The method of claim 1 including the step of forming closed loop ends on each of said split shaft members.
 4. The method of claim 1 including the step of forming hook ends on each of said split shaft members.
 5. The method of claim 1 wherein said cutting step forms two longitudinally split quarter sections on each of said split shaft members.
 6. The method of claim 1 wherein said cutting step forms a longitudinally split half section on each of said split shaft members. 